The present invention relates to a hybrid integrated circuit device and manufacturing method thereof, and more particularly to a hybrid integrated circuit device having a resin seal body formed on a hybrid integrated circuit substrate by transfer molding and to a manufacturing method thereof.
Generally, there are, principally, two methods of sealing employed for hybrid integrated circuit devices.
The first method employs member having such a form as placing a lid, generally called a case member, on a hybrid integrated circuit substrate mounted with circuit elements of semiconductor chips or the like. This structure includes a hollow structure or that having a resin separately filled therein.
The second method is injection molding as a process to mold semiconductor ICs. This is described, e.g. in Japanese Patent Publication No. H11-330317. The injection molding generally uses thermoplastic resin. For example, the resin heated at 300° C. is injected under a high injection pressure and poured into a mold at one time, whereby the resin is molded. Since a resin polymerization time is not required after pouring a resin into a mold, there is a merit to shorten the operation time as compared with transfer molding.
Explanation will be made on a method of manufacturing a conventional hybrid integrated circuit device using injection molding, with reference to FIGS. 10 to 13C.
First, an aluminum (hereinafter, referred to as A1) substrate 1 is employed as a metal substrate as shown in FIG. 10, in order for explanation.
The A1 substrate 1 is anodized in its surface. Furthermore, a resin 2 having an excellent insulation property is formed on the entire surface of the anodized A1 substrate 1. However, the oxide may be omitted where voltage resistance is not taken into consideration.
As shown in FIGS. 13B and 13C, a resin seal body 10 is formed by a support member 10a and a thermoplastic resin. Namely, a substrate 1 mounted on the support member 10a is covered with thermoplastic resin by injection molding. The support member 10a and the thermoplastic resin have an abutment region. The abutment region of support member 10a is fused by the poured hot thermoplastic resin, thereby realizing a full-mold structure as shown in FIG. 10.
Herein, the thermoplastic resin adopted is a resin called PPS (polyphenyl sulfide).
The injection temperature of thermoplastic resin is as high as 300° C. Consequently, there is a problem that solder 12 be fused by the hot resin thereby causing poor soldering. For this reason, an overcoat 9 is formed by potting a thermosetting resin (e.g. epoxy resin) in a manner previously covering solder joints, metal fine wires 7, active elements 5 and passive elements 6. Due to this, the fine wires (approximately 30-80μm) particularly are prevented from being fallen down and broken under an injection resin pressure during forming with a thermoplastic resin.
The resin seal body 10 is formed through two stages shown in FIGS. 13B and 13C. In the first stage, a gap is provided at between a backside of the substrate 1 and a mold die. The support member 10a is placed on the backside of the substrate, in consideration of securing a thickness at a backside of the substrate 1 upon poring a resin under a high pressure into the gap. In the second stage, the substrate 1 mounted on the support member 10a is covered with a thermoplastic resin by injection molding. In the abutment region between the support member 10a and the thermoplastic resin, the abutment region of the support member 10a is fused by the poured hot thermoplastic resin thereby realizing a full-mold structure. Herein, the thermoplastic resin on the support member 10a preferably has an equivalent thermal expansion to that of the substrate 1.
Next, explanation will be made on a conventional method of manufacturing a hybrid integrated circuit device using injection molding, with reference to FIGS. 11 to 13C.
FIG. 11 is a flowchart, including a metal substrate preparing process, an insulating layer forming process, a Cu foil pressure-laying process, a partial Ni plating process, a Cu foil etching process, a die bonding process, a wire bonding process, a potting process, a lead connection process, a support member attaching process, an injection mold process and a lead cutting process.
FIGS. 12A to 13C show the sectional views of the processes. Note that the processes, that are apparent without showing, are omittedly shown.
At first, FIGS. 12A and 12B show a metal substrate preparing process, an insulating layer forming process, a Cu foil pressure-laying process, a partial Ni plating process and a Cu foil etching process.
In the metal substrate preparing process, prepared is a substrate in consideration of its property of heat dissipation, substrate strength, substrate shield and the like. This example uses an Al substrate 1 having a thickness, e.g. of approximately 1.5 mm, excellent in heat dissipation property.
Next, a resin 2 excellent in insulation property is further formed over the entire surface of the aluminum substrate 1. On the insulating resin 2, a Cu conductor foil 3 is pressure-laid to constitute a hybrid integrated circuit. On the Cu foil 3, an Ni plating 4 is provided over the entire surface in consideration of adhesion to a metal fine wire 7 electrically connecting between the Cu foil 3 as a lead-out electrode and an active element 5.
Thereafter, a known screen-printing is used to form Ni plating 4a and a conductive path 3a. 
Next, FIG. 12C shows a die bonding process and a wire bonding process.
On the conductive path 3a formed in the preceding process, an active element 5 and a passive element 6 are mounted through a conductive paste such as a solder paste 12, thereby realizing a predetermined circuit.
Next, FIGS. 13A and 13B show a potting process, a lead connection process and a support member attaching process.
As shown in FIG. 13A, in the potting process, prior to a later injection mold process, potting is previously made with a thermosetting resin (e.g. epoxy resin) onto the solder junctions, metal fine wires 7, active elements 5 and passive elements 6, thereby forming an overcoat 9.
Next, prepared is an outer lead 8 for outputting and inputting signals from and to the hybrid integrated circuit. Thereafter, the outer lead 8 is connected to the external connection terminal 11 formed in a peripheral area of the substrate 1 through a solder 12.
Next, as shown in FIG. 13B, the hybrid integrated circuit substrate 1 connected with the outer lead 8 and the like is mounted on a support member 10a. By mounting the substrate 1 on the support member 10a, it is possible to secure a thickness of a resin seal body at a backside of the substrate 1 during injection molding as explained in the next process.
Next, FIG. 13C shows an injection mold process and a lead cutting process.
As shown in the figure, after potting is done with a thermosetting resin on the substrate 1 to form a overcoat 9, a resin seal body 10 is formed by injection molding. At this time, in the abutment region between the support member 10a and the thermoplastic resin, the abutment region of the support member 10a is fused by the injected hot thermoplastic resin and turned into a full-mold structured resin seal body 10.
Finally, the outer lead 8 is cut to a use purpose thereby adjusting the length of the outer lead 8.
By the above process, a hybrid integrated circuit device is completed as shown in FIG. 10.
On the other hand, in the semiconductor industry, it is a general practice to carry out a transfer mold process. In a hybrid integrated circuit device by the conventional transfer molding, a semiconductor chip is fixed on a leadframe, e.g. of Cu. The semiconductor chip and the lead are electrically connected through a gold wire (hereinafter, referred to as Au). This is because the impossibility of employing an Al fine wire in respect of its less elasticity and ready bendability and time-consumed bonding requiring ultrasonic waves. Consequently, there has not conventionally existed a hybrid integrated circuit device that is formed by one metal plate to have a circuit formed thereon and further the metal substrate wire-bonded by A1 fine wires is directly transfer-molded.
In a hybrid integrated circuit device of an injection mold type, there has been a need to prevent the metal fine wire 7 from being bent or broken under an injection pressure during molding, and the solder 12 from flowing at a temperature upon injection molding. For this reason, in the conventional structure shown in FIG. 10, the overcoat 9 due to potting has been adopted in order to cope with the foregoing problem.
However, because injection molding is carried out after potting a thermosetting resin (e.g. epoxy resin) to form an overcoat 9, there is a problem of consuming a material cost for thermosetting resin together with operation cost.
Meanwhile, in the hybrid integrated circuit device by the conventional transfer molding, a semiconductor chip or the like is fixed on an island. Accordingly, although the heat generated from the semiconductor chip or the like dissipates at the fixing region, there is a problem that there is a limitation in heat dissipating area resulting in poor heat dissipation.
Furthermore, because the wire bonding within the resin seal body uses Au wires resistive to resin injection pressure as noted above, it is not a current practice to carry out transfer molding with using Al fine wires. The A1 fine wire is readily bent due to the causes of a weak neck resulting from ultrasonic bonding and further too low elastic modulus to withstand under injection pressure.
Furthermore, in the case of integrally sealing hybrid integrated circuit substrates by transfer molding, there is a need to fix the hybrid integrated circuit substrate in horizontal and thickness directions within a mold die. There is a problem that such fixing member has not been developed as to withstand under an injection pressure during molding.